Electronic coupling coordinated vanadium nitride/magnesium oxide hetero-junction for accelerating oxygen reaction and long-life flexible zinc-air batteries

Designing highly active, durable, and cost-effective electrocatalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is explored as exciting research trends. However, a deep understanding of electrochemical performance enhancement is still a big challenge. Herein, we develop a well-defined vanadium nitride/magnesium oxide (VN/MgO) heterostructure on nitrogen-doped carbon frameworks (VM-NC) with enhanced active sites and tunable electronic structure. The synergistic effect at VN/MgO interfaces facilitates the charge-transfer rate, increases the active sites, and promotes OER/ORR kinetics in an alkaline medium. Theoretical studies suggest that the tuning of electronic structure in VN-MgO effectively boosts the conductivity and catalytic activity of VM-NC. The catalyst delivers an excellent half-wave potential of ≈ 0.852 V for ORR and a low overpotential of ≈ 253 mV for OER. Furthermore, VM-NC-based zinc-air cells (ZACs) exhibit high peak power-density and ultralong cycle-life. The quasi-solid state flexible ZACs present excellent flexibility with different bending states and outstanding electrochemical performance.